The DEFINER library contains an extension to Common Lisp that allows programmer to nicely reuse some common "definition" idioms.

Many CL packages extend the language by adding a slew of macros that look like the following:

(defsomething ...)

and/or

(define-something-else ...)

Well, wouldn't it be nice to have a more controlled way to do that? DEFINER is for you. A quick hack where we extend CL to define more complex definition forms.

The idea is to provide a general macro def and a specialized generic function for further extensions.

The end result is to make Common Lisp definitions look like Python. Of course, with a twist. def is written completely in Common Lisp, and in Python you need to hack the parser to extend the behavior of def.